Compressed air dehydration system with desiccant reactivating means



Oct- 18, 1966 G. c. KAUER, JR., ETAL 3,279,151

COMPRESSED AIR DEHYDRATION SYSTEM WITH DESICGANT REACTIVATING MEANS 2Sheets-Sheet 1 Filed March 25, 1964 COMPRESSOR INVENTORS LOU/S E. BROOKSBY GEORGE C. KAUER, JP.

A 7' TOR/VEV Oct- 18, 1966 G. c. KAUER, JR.. ETAL 3,279,151

COMPRESSED AIR DEHYDRATION SYSTEM WITH DESICCANT REACTIVATING MEANSFiled March 25, 1964 2 Sheets-Sheet 2 Oumar 75 ll V18 Arrow/ey UnitedStates Patent O CMPRESSED AIR DEHYDRATIGN SYSTEM WITH DESICCANTREACTIVATING MEANS George C. Kauer, Jr., Westbury, and Louis E. Brooks,Great Neck, N.Y., assignors to Air Techniques, Inc.,

New Hyde Park, N.Y., a corporation of New York Filed Mar. 23, 1964, Ser.No. 353,850 Claims. (Cl. 55-26) This applic-ation is acontinuation-in-part of our application Serial No. 250,422, filedJanuary 9, 1963.

This invention relates generally to apparatus for drying compressedgases, and more particularly to a cornpressed air dehydration system inwhich means are provided for reactivating, upon command, the systemsdesiccant, or drying agent.

It is one object of the present invention to provide improved means toreactivate, that is to say, remove absorbed water vapor, from thedesiccant in a compressed air dehydration system.

It is another object of the invention to enable compressed air to beused by supplying it from the compressed air source lduring reactivationof the desiccant, if such use is needed.

Another object of the invention is to provide for the supply of thecompressed air during the reactivation cycle of the desiccant to thecompressed `air operated instrument without appreciable reduction of the`air pressure.

Another object is to provide for automatically initiating thereactivating cycle when the air compressor is initially put intooperation under manual control.

A further object of the invention is to reactivate the desiccantautomatically each time the compressor is started.

These and other objects of the invention are accomplished, broadly, bythe provision of a chamberfor containing a desiccant, means for passinga compressed gas to be dried through the desiccant chamber and fromthere to a compressed gas utilization device, and means for expellingthe moisture absorbed by the desiccant from the chamber.

One feature of the invention resides in an arrangement for drawingcompressed gas from the system and if needed, during the interval inwhich the moisture is being expelled from the desiccant chamber.

Another feature of the invention involves an automatic control unitwhich transforms the absorbed moisture in the desiccant to vapor andexhaust the vapor into the atmosphere each time the systems compressoris turned Still another feature of the invention pertains to anarrangement for passing the moist compressed gas through the desiccantchamber in one direction for the purpose of drying the gas, and forpassing a thin stream of the gas through the chamber in the oppositedirection for the purpose of expelling the moisture absorbed by thedesiccant into the atmosphere.

The foregoing and various other objects, features and advantages of theinvention will be more thoroughly understood by reference to thefollowing detailed description of a preferred embodiment of theinvention in conjunction with the accompanying drawing of which:

FIG. 1 is a schematic View, partially in section of a compressed gasdrying system constructed in accordance with the invention;

FIG. 2 is one embodiment of an electrical control system for operatingthe drying system;

FIG. 3 is another embodiment of an electrical control system foroperating the drying system;

FIG. 4 is a view similar to FIG. l, showing another preferred embodimentof the invention; and

3,279,151 Patented Oct. 18, 1966 ice FIG. 5 is a View similar to FIG. 3,showing another preferred electrical -control system for the compressedair supply apparatus.

With reference to FIG. 1 of the drawing, a compressed air drying systemis shown in which compressed air from the tank of a conventionalcompressor (not shown) is passed through an inlet T joint 1, aconnecting pipe 2, and ports a and b of two-way solenoid operated valve3 to a flow-through desiccant chamber 4 for removing moisture from thegas, and from there as suciently dry compressed air through a T joint54, an elbow joint 5, a check valve `6 and an outlet T joint 7 to acompressed air utilization device, for example, a dental drill (notshown). As shown, desiccant chamber 4 basically comprises an externallythreaded hollow cylinder having shallow internal shoulders 8 at eitherend thereof lfor supporting screens 9. Internally threaded caps 10`enclose the chamber 4 at either end and secure screens 9 in placeagainst their respectiveshoulders 8. A desiccant, shown generally as 11,which by way of illustration and not restriction may be silica gel oractivate-d alumina, is contained in chamber 4 between screens 9.Associated with chamber 4 is a heating band 12 which is electricallyconnected to the control circuitry of the system by conductors 13.

Solenoid operated valve 3 comprises three ports; namely, port a whichadmits air from the compressor tank, port b which is connected to onecap 10 of the desiccant chamber, and port c through which water vaporfrom the desiccant chamber is exhausted to the atmosphere as will beexplained in greater ydetail hereinafter. As shown, solenoid operatedvalve 3 is essentially in the shape of a T and includes a pair of walls13 and 14 for internally separating from each other the arm of the Tterminating in port c from the arms of the T terminating in ports ,a andb. A passage 15 permanently interconnects the latter two -arms of thevalve. Longitudinally disposed in the arm of the valve terminating inport a is a cylindrical core 16 which tapers sharply in conical fashionto valve stops 17 and 18 at opposite ends of the core. A disc 19,parallel to wall 14 and having an aperture 20 therein tapered to receivethe valve stop 18, is disposed adjacent to port a. Wall 14 includes anaperture 21 situated opposite aperture 20 and tapered to receive valvestop 17. Posts 22, which project from the walls of the valve, form aguideway in which valve core 15 is shifted between apertures 20 and 21under the control of solenoid 23 which is electrically coupled to thecontrol circuitry by conductors 24.

Solenoid operated valve 3 is oriented so that when solenoid 243 isdeenergized, the combined forces of a non-illustrated biasing spring,and of the air pressure from the compressor tank, force valve stop 17into aperture 21, as shown in the drawing, thereby allowing air from thecompressor tank to ow from port a to port b through passage 15, andthence into the desiccant chamber for drying. When solenoid 23 isenergized, as will be explained hereinafter, core 16 is longitudinallyshifted such that aperture 20 is closed by valve stop .18 and watervapor from the desiccant chamber is allowed to exhaust to the atmospherethrough port b, passage 15, aperture 21 and port c.

Connected to the stems 25 and 26 of T joints 1 and 7 is a pressureresponsive by-pass valve 27 comprising an inlet duct 2-8, an outlet duct29 and a valve opening 30 separating these ducts. Seated in valveopening 30 is a valve 3 1 supported from below by a compression spring32 and from above by a rod 33 which bears against a diaphragm 34. Assho-wn, the under surface of diaphragm 34 is open to outlet duct 29.Valve `27 also includes a pressure chamber 35 situated above diaphragm34 which is lled with air from the compressor tank lvia a tap 3 36. Itwill be apparent to those familiar with pressure responsive valves suchas 27 that when the pressure above diaphragm 34 is substantially equalto the pressure be- I low the diaphragm, that is to say, when thepressures at the inlet and outlet ducts are substantially equal, theforce of the diaphragm on rod 33 tending to open valve 31 is nullifiedand spring 32 urges valve 31 to closed position. However, when thepressure at outlet duct v29 falls `below the pressure at inlet duct 28,the greater pressure above diaphragm 34 forces rod 33 to unseat valve31, and thereby opens the valve through aperture 30, there beingsufficient clearance under said diaphragm so that it can flex to openthe valve. It should be evident to one skilled in the art that numerousother type Valves could be substituted for pressure sensitive valve 27without departing from the principles of the invention. For example, asolenoid operated valve such as valve 3, only modified such that port ais permanently closed, would be equally suitable.

With solenoid 23 deenergized the valve would be closed, and with thesolenoid operated the valve would be open, thereby allowing the passageof air between ports b and c.

Connected in line 37, which joins outlet duct 29 of valve 27 to stem 26of T joint 7, is a T joint 38. The stems of T joints 54 and 38 areconnected by a two layer filter 39 and dics 40 which provides a smallorifice for filtered air In a prises a loosely packed first layer 41 anda more tightly packed second layer 42 both of pressed copper wool.

Disc 40 is secured in the line yby being interposed, along with asuitable sealing material, between -two flanged pipe members. The pipemembers are fastened together by an internally threaded coupler 43 whichbears against the face of one flange and is threaded upon the rim of theother flange so that turning of the coupler draws the flanges together.A suitably sized orifice is provided in disc 40 by puncturing the discand inserting .therein a thin Y wire filament `45.

The compressed air drying system of FIG. l operates in two distinctcycles, a drying cycle and a desiccant reactivation cycle. During thedrying cycle solenoid 23 of valve 3 is deenergized, thereby allowingcore 16 to assume the position shown with aperture 20 open and aperture21 closed. Consequently, moist air from the cornpressor tank passesthrough T joint 1, connecting line 2,

port a, aperture 20, passage 15, port b, desiccant chamber '4 wheremoisture is removed, T joint 54, elbow 5, check valve 6 and T joint 7 tothe compressed air utilizer.

Since only a slight drop in pressure is encountered around :the loopjust described, the pressures at the inlet and 4 outlet ducts, 28 and29, respectively, of bypass valve 27 are substantially equal, andconsequently valve 27 is closed by the force of spring 32. Hence, duringthe drying cycle all air from the compressor tank is dried in thedesiccant chamber before utilization.

During the reactivation cycle, both solenoid 23 and heating band 12 areenergized, as will be explained hereinafter. Energization of solenoid 23shifts core 16 along l the guideway provided by posts 22 such thatapertures 20 and 2i1 are closed and opened, respectively. Consequently,desiccant chamber `4 is open to the atmosphere through port b, passage15, aperture 21 and port c, and the pressure at T joint 7 begins to dropaccordingly. As the pressure at T joint 7 drops, a pressure differentialis created across diaphragm 34, and valve 27 opens. During thereactivating cycle, the compressed air utilizer is normally not operatedbut if it is essential to operate the utilizer, compressed air can bedrawn for that purpose from the compressor through valve 27 and conduit37 as later explained.

Energization of heating band 12 raises the temperature of desiccant 11and transforms the absorbed moisture into water vapor. This vapor isthen driven from chamber 4 and exhausted to the atmosphere through portsb and c of the solenoid operated valve by means of the small stream offiltered air which bleeds through the orifice in disc 43. Approximatelymidway in the reactivation cycle heating band 12 is deenergized so thatdesiccant 11 is restored to a suitable temperature for moistureabsorption when the drying cycle commences. When the reactivation cycleterminates, solenoid 23 is deenergized, allowing valve stop 17 of core16 to once again block aperture 21 and concomitantly opening ports b andc to each other.

One embodiment of a control unit capable of supplying appropriatelytimed operating potentials to solenoid 23 and heating band 12 is shownin FIG. 2. The control unit comprises line 45 which is connectablethrough armature 46 of a first switch to heating band 12 which is inseries with a normally closed thermal sensitive bimetallic switch 47,and through armature 48 of a second switch to the winding of solenoid 23which is in series with a rectifier 49. A pilot lamp 50 is disposed inparallel with the rectifier-solenoid combination so as to indicate whenthe system is operating in the reactivation cycle. The current supplyfor line 45 may comprise the usual wall outlet providing volt 60cycle/sec. power. As shown, the actuation of armatures 46 and 48 iscontrolled jointly by a conventional spring wound timer mechanism 51. Inthe embodiment of the invention described herein, mechanism 51 is athirty minute timer which closes the armatures 46 and 48 at the start ofa timing cycle, opens armature 46 at the end of fifteen minutes, ormidway during a `complete timer cycle, and opens armature 48 uponcompletion of the cycle. Numerous devices answering the foregoingdescription of timer mechanism 51 are available commercially, andconsequently further explanation of such apparatus is believedunnecessary. v

Normally the system operates in the drying cycle, that is to say, witharmatures 46 and 48 separated from their associated contacts, andtherefore with heating band 12 and solenoid 23 deenergized. When it isdesired to reactivate the desiccant, timer 51 is wound to the thirtyminute mark, whereupon armatures 46 and 48 close with their associatedcontacts. Accordingly, heating band 12 is energized through normallyclosed thermostat switch 47 and transforms the absorbed moisture in thedesiccant to vapor. Concurrently, solenoid 23 is energized throughrectifier 49, thereby opening bypass valve 27 (FIG. 1) and providing astream of filtered air through the orifice in disc 40 with which thevapor in the desiccant chamber 4 is driven by a thin stream ofcompressed air t-o the atmosphere through port c of valve 3. Thermostatswitch 47 is so situated to regula-te the temperature of heating band 12by interrupting the flow of current in conductors 13 when thetemperature of the band rises above a predetermined level. Switch 47opens and interrupts the heating operation, permitting the desiccant tocool gradually to a temperature suitable for drying. At the end offifteen minutes contact 46 opens and at the end of thirty minutescontact 48 opens, thereby deenergizing solenoid 23 and shifting thesystem back to the drying cycle. It will be observed that during thereactivation cycle, compressed air, although moist, is available to thecompressed air utilizer via bypass valve 27,

i but normally the dentist or other operator would not use the utilizerand hence no considera-ble flow of compressed air from the source wouldoccur.

FIG. 3 illustrates a fully automatic control unit which initiates areactivation cycle each time the systems compressor is initiallystarted. As shown, both the control unit and the compressor motor arepowered from the same line 45 and both commence operation in response tothe closure of manually operated switch 55. As its timing device thecontrol unit of FIG. 3 includes a motor 56, the output shaft 57 of whichis suitably geared to revolve at the rate of one revolution per thirtyminutes. Coaxially mounted on shaft 57 of timing motor 56 are a pair ofcams 58 and 59. Cam 58 is substantially circular, but is interruptedperipherally by a sharp valley 60. Cam 59 is essentially a two-phase camcharacterized by a raised lobe 61 extending approximately 180 degreesaround its perimeter. Follower rods 62 and 63 ride the rims of cams 58and 59, respectively, and operate make contacts 64 and 65. Cams 58 and59 are fixedly secured to shaft 57 such that when motor 56 is at rest,follower rod 62 is positioned in valley 60 and follower rod 63 is at thefoot of the leading edge of raised lobe 61.

The motor 56 is connected to line 45 through normally closed breakcontacts 66 of a thermal switch 67, and the heating element of switch 67is connected directly across the line electrically behind switch 55. Apilot lamp 50 shunts motor 56 to indicate when the system is operatingin a reactivation cycle. As shown, make contacts 64, which areassociated with cam 58, are bridged across break contacts 66 of thermalswitch 67, and a rectifier 49 in series with solenoid 23 are bridgedacross motor 56. Make -contacts 65, associated with cam 59, the heatingband 12 and its associated bimetallic thermostat 47, all connected inseries, are also bridged across the line electrically behind switch 55.

The air compressor is started by closing switch 55, and simultaneously areactivation cycle is commenced by the introduction of current intomotor 56, pilot lamp 50 and solenoid 23 through break contacts 66 ofthermal switch 67. Almost immediately thereafter shaft 57 begins to turncams 58 and 59, thereby closing ymake contacts 64 and `65. Accordingly,current energizes heating band 12 which begins to transform theaccumulated moisture in the desiccant into vapor. Shortly after switch55 is closed, the heating element of switch 67 causes break contacts 66to separate. Nevertheless, current is maintained in the motor, the pilotlamp and solenoid 23 through make contacts 64. As in the embodiment ofFIG. 2, thermostat 47 maintains the temperature of heating band 12 at afairly constant level.

After fifteen minutes have elapsed, cam 59 has rotated 180 degrees andfollower rod 63 falls, thereby separating make contacts 65. Thereafter,the desiccant begins to cool gradually to a temperature suitable for thedrying cycle. At the end of thirty minutes, cam 58 has completed a fullrevolution and follower rod 62 falls into valley 60. As a result, makecontacts 64 separate, thereby deenergizin'g the timing motor, the pilotlamp and solenoid valve 23. In this manner the system shifts from areactivation to a drying cycle of operation. It will be observed thatsince switch 55 is still closed after completion of the reactivationcycle, break conta-cts 66 of thermal switch 67 remain separated, andthus prevent the recurrence of a reactivation cycle. However, each timethe compressor is started by closure of switch 55, provided thatcontacts 66 are also closed at this time, a reactivation cycle will becommenced.

Referring now to the apparatus of the embodiments of FIGS. 4 and 5, thesame may readily be seen to be structurally similar to the apparatus ofthe embodiments of FIGS. l, 2 and 3. To this effect, and for convenienceof description, corresponding structural components of the apparatus ofFIGS. 4 and 5 are identified by the same numerals utilized therefor inFIGS. l, 2 and 3, with the said numerals being primed in the latterfigures. Thus, for example, the desiccant 11 of FIG. l bears theidentifying number 11 in FIG. 4, while the timing motor 56 of FIG. 3bears the identifying number 56 in FIG. 5.

By-pass valve 27 is of significantly `different construction in theembodiment of FIG. 4, and comprises a housing 104 connected as shownbetween connecting pipes 215 and 37', respectively. A stepped bore 105is formed in the said housing and includes passages 114 and 116,respectively, extending therefrom as shown for connection with the saidconnecting pipes. A stepped piston 106, including piston rings 110 and112 positioned thereon, and a valve closure member 108 supported thereinin the ,depicted marmer, is `slidably positioned as shown within thesaid bore 105 and is movable therein from the depicted position in whichthe said valve closure member 108 is effective to prevent fluid owcommunication between passages 114 and 116, to a second position inwhich such communication takes place whereby connecting pipe 25 isplaced in fluid flow communication through the said valve passages withconnecting pipe 37 An arcuate cut-away portion 118 is formed as shown inhousing 104 just above valve member 108 and functions to enable thepressure in connecting pipe 25 to act upon the portion of the said valvemember and piston 106 positioned therebelow. A T-litting 100 is attachedas shown to the -outlet of the desiccant chamber 4 by threaded endcap 10extending thereover, and includes a flow passage 99 formed therein, anda conduit 102 which extends therefrom into uid flow communication withthe larger portion of bore 105. Thus may be understood whereby thepressure at the T-itting side of the desiccant chamber 4 is communicatedto the larger portion of the said bore.

A housing member 119 is provided and includes communicating ilowpassages 120, 122, 123 and 124, formed therein as shown; with each of`said flow passages being in fluid ow communication with the outlet 149to the compressed gas utilization device. Check valve 6 is positioned asshown intermediate flow passages 120 and 122 whereby may be understoodthat fluid flow therethrough may take place only from the former to thelatter flow passage. T-tting 100 is threadably attached as shown to thesaid housing 119 with flow passage 99 in fluid ilow communication withow passage 120 to thus provide for the flow of gas from the loutlet ofthe desiccant chamber 4 to the outlet 149 of the housing 119.

Flow passages 123 and 124 may be seen to provide a by-pass around thesaid check valve 6', with the latter of the said llow passages includingfilters 41 and 42 and disc 40', including restricted orice 49 formedtherein, and positioned as shown in the said latter flow passage t-osignificantly reduce fluid ow therethrough in either direction.

In operation, with solenoid operated valve 3 deenergized and valvemember 16 accordingly positioned as shown, it may thus be understoodwhereby compressed gas will flow to the said valve from compressed gasinlet 83 through connecting pipe 2', flow therethrough through lopenports a' and b' thereof, flow through desiccant chamber 4 and throughilow passage 99 in T-titting 100 and flow passages 120 and 122 inhousing 119 respectively, to the outlet 149 to the compres-sed airutilizer. Some of the initial portion of the said compressed gas will ofcourse ow from T-fitting 100 to the larger portion of bore 105 invhousing 104 to bias piston 106 to the depicted position thereof,whereby valve member 108 will be maintained in the depicted closedposition thereof to prevent fluid flow from connecting pipe 25 throughthe bypass valve 27' to connecting pipe 37.

With the said solenoid operated valve 3i in the energized conditionthereof, port a' will be closed by valve stop 18 and ports b and c openand in uid iiow communication. Thus, compressed gas entering at theinlet 83 from the compressor tank will be unable to flow from connectingpipe 2' through the said solenoid operated valve, whereby no appreciablepositive pressure will be created in the larger portion of bore 105 ofthe by-pass valve 27. The compressed gas will, however, ow readilythrough connecting pipe 25 to fill cut-away portion 118 of bypass valvehousing 104 and act upon valve member 108i, piston 106, and piston ring110, to force the said piston from the depicted position thereof to openvalve 108 and place valve flow passages 114 and 116 in fluid flowcommunication to allow the compressed gas to flow from connecting pipe25 through the said flow passages to connecting pipe 37', and to iiowtherefrom through iiow passage 125 in housing 119 to the outlet 149 tothe compressed air utilizer. Check valve 6 will Y prevent the flow ofany of the compressed gas through housing ow passage 122 to housing flowpassage 120. A small portion of the gas will, however, flow throughpassage 123, lters 41' and 112" and orice 49 in passage '124, passage 99in the T-tting 100, the desiccant charnber 4', and open ports b' and cof the solenoid operated valve, to exhaust to atmosphere from the latterport.

may be understood whereby the drive motor 150 and the indicating light50' will be energized at all times during the on position of the mainpower switch 55'. A timing motor 56' is connected between the lines L-lland L-Z by leads 168 and 162, respectively. Drive shaft 57 extends fromthe said timing motor and functions, through slip clutch 164, to drivetiming cam shaft 163 which includes timing cams 58' and 59' xedlypositioned thereon. A positioning knob 166 is axed to the remoteextremity of the timing cam shaft to enable the manual adjustment of thepositions of the timing cams 58' and 59', without requiring rotation oftiming motor 56' due to the action of slip clutch 164.

The windings 23' of solenoid operated valve 3' are connected across thelines by leads 172, 170 and 160, re-

` spectively. Alternatively, the said windings are connectable acrossthe lines by leads 172 and 173, timing cam actuated switch 64', and lead174. Heating band 12' is connectable across the lines by leads 178 and179, timing cam operated switch 65', and lead 176. A relay is generallyindicated at 179 with the coil 180 thereof connectable across the linesthrough lead 181, contacts 184 and 194 of the said relay, and lead 182.Alternatively, the said coil is connectable across the said lines bylead 181, relay contacts 186 and 192, lead 187, lead 179, timer actuatedswitch 65', and lead 176. A third set of relay contacts 188 and 189 isconnected as shown in lead 160 to control the energization of timingmotor 56' therethrough.

The respective timer operated switches and relay contacts are depictedin FIG. 5 in the positions thereof at the commencement of compressoroperation. Thus, upon the closing of manually operable switch 55' toenergize the said control circuit through lines L-1 and L-2, the circuitto the timing motor 56' will be completed through lead 160, relaycontacts 189 and 188, and lead 162 to thus energize the said timingmotor and commence rotation of the timing cams 58' and 59' in thecounterclockwise direction as seen in the subject figure. The windings23' of solenoid operated valve 3' will also be energized through lead160, relay contacts 189 and 188, lead 170 and lead 172 to shift thevalve member 16' of the said solenoid operated valve from thede-energized position thereof depicted in FIG. 4 to the energizedposition thereof, whereby port a' will be closed and ports b and c'opened and in fluid flow communication with the atmosphere. Thus, and inthe manner described in detail hereinabove, by-pass valve Z7' will beopened and the compressed gas from the compressor tank will commence toflow directly to the outlet 149 to the compressed air utilizer throughconnecting pipe 25', the now open by-pass valve 27', connecting pipe 37'and housing flow passage 125. A small portion of the gas will alsocommence to ow through ow passages 123, 124, 120, and 99, through thedesiccant chamber 4' and out to atmosphere through the now open ports b'and c' of the solenoid operated valve. Almost immediately upon theenergization of the circuit, and commencement of rotation 0f the timingcams 58' and 59', timer actuated Cil switch 64' is closed as camfollower 62' rides out of cam notch 611'. Shortly thereafter, the highportion 61' of cam 59' will coact with cam follower 63 to close timeractuated switch 65' to thus energize heater band 12' through lead 176,the said timer operated switch 65', lead 179 and lead 178. This will, ofcourse, commence to vaporize the moisture collected in the desiccant11', in the manner described in detail hereinabove, for the removalthereof to atmosphere through ports b' and c' by the small portion ofthe compressed gas now owing through the desiccant chamber.

The closing of timer actuated switch 65' will also function to energizecoil 180 of relay 179 through lead 176,

the said switch, lead 179, lead 187, relay contacts 192 and 186, andlead 181. As the relay coil is energized, contacts 188 thereof areopened to thus break one of the energization paths to the said timingmotor 56'. The alternative energization path to the said timing motorthrough switch 64' as described hereinabove remains completed however,whereby the timing motor continues to operate. As the relay coil isenergized, this also tends to break relay contacts 186 and 192 and tomake relay contacts 184 and 194, it being understood, however, thatrelay contacts 184 and 194 are specifically designed to make beforerelay contacts 186 and 192 break Thus is made clear that the saidshifting of the said relay contacts at this point will have no effectupon the energization of relay coil 18) other than to shift theenergization thereof to the path including leads 182 and 181. Theapparatus will continue to function in this manner until the low side oftiming cam 59' is again presented to switch actuator 63' of switch 65',whereupon the said switch will open to break the energization circuit tothe heating band 12 and the said band will commence to cool, while theflow of compressed gas through the desiccant chamber 4' from T-shapedfitting 100 to atmosphere through 4the open ports b' and c' of thesolenoid operated valve 3' continues because the said solenoid operatedvalve remains energized through the continued energization of thewinding 23' thereof. Reactivation operation with the heating band 12'de-energized, and cooling, continues until notch 69' of timing cam 58 isagain presented to switch actuator 62' at which point switch 64' isagain opened to break the remaining energization circuits to winding 23'of the solenoid operated valve 3', and timing motor 56', respectively.Thus the former becomes deenergized enabling the valve member 16 toreturn to the position thereof depicted in FIG. l, and timing motor 56'comes to a halt. The timing cams 58' and 59' thus halt in the depictedpositions thereof. Relay coil 180 remains energized at this time throughline L-1, lead 182, relay contacts 194 and 184, lead 181, the coil andline L-2, to thus maintain relay contacts 188 in the open positionthereof to prevent further energization of the said timing motor orsolenoid valve windings. Thus, it may be understood whereby only themanual opening of main power switch 55' will result in de-energizationof relay coil 180 to in turn reclose relay contacts 188 tomake possiblerepetition of the above described reactivation cycle upon the reclosingof main power switch 55' as described hereinabove.

It will be understood in all cases that the embodiments and arrangementsof the invention described herein are merely illustrative, and shouldnot be taken to restrict or limit in any manner the true spirit andscope of the invention.

What is claimed is:

1. A method of operation of a gas drying system, which system includes asource of compressed gas comprising a gas compressor which may bemanually started, a gas drying chamber containing a desiccant, and gasutilization means, comprising the steps of: normally passing arelatively large stream of compressed gas from said source through saidchamber in a rst direction to said utilization means, whereby saiddesiccant absorbs moisture from said gas; at intervals, providing areactivation period comprising discontinuing the fiow of gas throughsaid chamber in said rst direction, heating the desiccant to vaporizeabsorbed moisture, passing a relatively small stream of compressed gasfrom said source through said chamber in a second, opposite, directionto a vent, thereby expelling the vaporized moisture from said chamberand said system, and providing, upon demand, a stream of compressed gasfrom said source, bypassing said chamber, to said utilization means,said reactivation period being provided immediately subsequent to eachtime that said gas compressor is started and before any gas hom said gascompressor is passed through said chamber in said first direction.

2. A compressed gas drying system comprising compressor means providinga source of compressed gas for a compressed gas utilization device,means providing first and second ducts for alternatively conveying saidgas to said device, said first duct comprising a chamber containing adesiccant through which said gas is passed, whereby moisture in said gasis transferred to said desiccant, electric circuit means and valve meansoperated thereby for concurrently starting said compressor means andblocking said first duct to the conveyance of gas to said utilizationdevice, means for developing a stream of gas when said first duct isblocked, and reactivation means operative when said first duct isblocked to expel said transferred moisture from said chamber, saidreactivation means comprising heating means other than the heat ofadsorption and operatively associated with said chamber for vaporizingsaid transferred moisture in said chamber and means for passing saidstream of gas through said chamber thereby to exhaust the vapor; saidcircuit means including a solenoid winding for operating said valvemeans, and means including a manually adjustable timer and a thermalswitch for regulating the heating period, said adjustable timer beingalso operable independently of said thermal switch to control theenergization and deenergization of said solenoid winding.

3. A compressed gas drying system in accordance with claim 2 whereinsaid timer comprises a timing motor, first and second switches operatedby said timing motor, said first switch being operative in conjunctionwith said valve to block said first duct and said second switch beingoperative to energize said heating means, a third switch forsimultaneously starting said compressor means and said timing motor, andmeans coupled to said timing motor for operating said first and secondswitches for different periods of time.

4. A compressed gas drying system comprising compressor means providinga source of compressed gas for a compressed gas utilization device,means providing first and second ducts for alternatively conveying saidgas to said device, said first duct comprising a chamber containing adesiccant through which said gas is passed, whereby moisture in said gasis transferred to said desiccant, electric circuit means and valve meansoperated thereby for concurrently starting said compressor means andblocking said rst duct to the conveyance of gas to said utilizationdevice, means for developing a stream of gas when said first duct isblocked, and reactivation means operative when said first duct isblocked to expel said transferred moisture from said chamber, saidreactivation means comprising heating means other than heat ofadsorption and operatively associated with said chamber for vaporizingsaid transferred moisture in said chamber and means for passing saidstream of gas through said chamber thereby to exhaust the vapor, saidcircuit means comprising a timing motor and first and second switchesoperable to control the energization thereof with said second switchalso being operable, in conjunction with said Valve means, to block saidfirst duct, third switch means operable to control the energization ofsaid heating means, and means coupled to said timing motor for operatingsaid second and third switches for different periods of time, and relaymeans controlled by said third switch means and in turn operable tocontrol the operation of said first switch means.

5. Apparatus according to claim 4 wherein said valve means comprises amulti-port valve disposed in said first duct, said valve having a firstport coupled to said source of compressed gas, a second port coupled tosaid chamber, a third port coupled to an exhaust passageway, and meansfor alternatively closing said first and third ports; a bypass valvedisposed in said second duct having an inlet coupled to said source andan outlet and a third duct connecting said first duct and said outlet ofsaid bypass valve, and serving as said means for developing and passinga stream of gas through said chamber; whereby when said first port isclosed said bypass valve is open, and when said third port is closedsaid bypass valve is closed.

References Cited by the Examiner UNITED STATES PATENTS Re. 18,831 5/1933Fleisher 55-20 869,731 10/1907 Richardson 137-509 1,620,582 3/1927Thrush 137--510 1,939,695 12/1933 Hasche. 1,948,779 2/1934 Abbott et al.55--31 2,058,919 10/1936 Sewell 55-387 X 2,124,932 7/1938 Stark et al.55--162 X 2,309,075 1/1943 Hill 55-35 X 2,322,603 6/1943 Thumim et al.55-33 X 2,356,890 8/1944 Schulze 55-62 X 2,440,326 4/ 1948 Gadman 55-179X 2,494,644 1/ 1950 Clement 55-33 2,535,854 12/1950 Hertrich 188--1512,600,435 6/ 1952 Shapiro 62--474 X 2,633,928 4/1953 Chamberlain 55--1622,830,672 4/1958 Asker 55-33 X 2,840,183 6/1958 George 55-309 X2,955,673 10/1960 Kennedy 55--33 X 2,989,971 6/ 1961 Valentine 137509 X3,016,978 1/1962 Hull 55-161 X 3,030,798 4/ 1962 Lichtenfels 73-23.13,080,693 3/1963 Glass et al. 55-33 X 3,087,112 4/1963 Pfefferle 73-23.1X 3,147,095 9/1964 Kanuch 55-33 X 3,169,389 2/1965 Green et al. 73-23.13,182,435 5/1965 Axt 55-33 X 3,192,686 7/1965 Berkey et al 55--33 X3,203,771 8/1965 Brown et al. 23-281 3,225,517 12/1965 Wachsmuth 55--80X FOREIGN PATENTS 857,155 4/1940 France.

OTHER REFERENCES Anders Driline Bulletin R-34, Desomatic ProductsDivision of Atlantic Research Corporation, 11109 W. Broad St., FallsChurch, Va., copyright 1959, 6 pages.

Industrol Dynamic Dehumidifiers, Technical Bulletin Number 6551,Industrol Corporation, 472 Westfield Ave., East Rossette Park, NJ.,received, Patent Office, Ian. 25, 1962, 2 pages.

Kemp Oriad Dryers, Bulletin D-103, The C. M. Kemp Manufacturing Co., 405E. Oliver St., Baltimore 2, Md., copyright 1957, 6 pages.

Gas Chromatography Growing, Chemical and Engineering News, Apr. 9, 1956,pp. 1692-1696.

Fisher Scientific Company Technical Data Bulletin No. Revised TD-1l4,September 1960, l1 pages.

REUBEN FRIEDMAN, Primary Examiner.

D. TALBERT, Assistant Examiner.

1. A METHOD OF OPERATION OF A GAS DRYING SYSTEM, WHICH SYSTEM INCLUDES ASOURCE OF COMPRESSED GAS COMPRISING A GAS COMPRESSOR WHICH MAY BEMANUALLY STARTED, A GAS DRYING CHAMBER CONTAINING A DESICCANT, AND GASUTILIZATION MEANS, COMPRISING THE STEPS OF: NORMALLY PASSING ARELATIVELY LARGE STREAM OF COMPRESSED GAS FROM SAID SOURCE THROUGH SAIDCHAMBER IN A FIRST DIRECTION TO SAID UTILIZATION MEANS, WHEREBY SAIDDESICCANT ABSORBS MOISTURE FROM SAID GAS; AT INTERVALS, PROVIDING AREACTIVATION PERIOD COMPRISING DISCONTINUING THE FLOW OF GAS THROUGHSAID CHAMBER IN SAID FIRST DIRECTION, HEATING THE DESICCANT TO VAPORIZEABSORBED MOSITURE, PASSING A RELATIVELY SMALL STREAM OF COMPRESSED GASFROM SAID SOURCE THROUGH SAID CHAMBER IN A SECOND, OPPOSITE, DIRECTIONTO A VENT, THEREBY EXPELLING THE VAPORIZED MOISTURE FROM SAID CHAM-